Inase M, Sakai S T, Tanji J
Molecular and Cellular Neuroscience Section, Electrotechnical Laboratory, Tsukuba, Japan.
J Comp Neurol. 1996 Sep 16;373(2):283-96. doi: 10.1002/(SICI)1096-9861(19960916)373:2<283::AID-CNE10>3.0.CO;2-M.
The purpose of the present study was to determine if the cortical efferents from homologous body regions of the supplementary motor area (SMA) and the primary motor cortex (MI) project to separate or to overlapping regions in the striatum. In order to investigate the dual corticostriatal projections, we employed an anterograde double labeling paradigm in which two tracers could be simultaneously detected in the same histological section. Prior to the injections, the forelimb representation in the two cortical motor areas was identified by using intracortical microstimulation in four Japanese monkeys (Macaca fuscata). Multiple injections of biotinylated dextran amine (BDA) were made into the forelimb regions of MI and wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) was injected into the arm region of the SMA. In additional animals, the tracers were reversed such that BDA was injected into the SMA and WGA-HRP was injected into the MI. The tissue was processed sequentially using different chromogens in order to visualize both tracers in a single section. We analyzed the distribution of the ipsilateral anterograde label. The striatal labeling from each cortical area basically consisted of a wide band of patchy dense labeling interrupted by lighter labeling. The SMA striatal projections were located mainly within the putamen, distributing from the level of the anterior commissure to the most posterior extent of the putamen. At an intermediate level, the label spread obliquely from the ventrolateral edge of the putamen dorsomedially as far as the lateral edge of the caudate nucleus. The label from the MI was observed in comparable portions of the putamen, although the SMA projections were shifted more anterior and dorsomedial to the MI projections and the heaviest projections from the SMA and the MI were separately located. On the basis of the double anterograde labeling technique, we found considerable overlap mainly in the central portion of the putamen from the SMA and MI forelimb representation. These results suggest that the homologous body regions of the SMA and MI send widespread, and substantially overlapping projections, to portions of the striatum.
本研究的目的是确定辅助运动区（SMA）和初级运动皮层（MI）同源身体区域的皮质传出纤维是否投射到纹状体中的不同区域或重叠区域。为了研究双重皮质纹状体投射，我们采用了顺行双重标记范式，其中可以在同一组织学切片中同时检测到两种示踪剂。在注射之前，通过对四只日本猕猴（食蟹猴）进行皮质内微刺激来确定两个皮质运动区中的前肢代表区。将生物素化葡聚糖胺（BDA）多次注射到MI的前肢区域，并将小麦胚芽凝集素结合辣根过氧化物酶（WGA-HRP）注射到SMA的臂部区域。在其他动物中，示踪剂进行了互换，即BDA注射到SMA中，WGA-HRP注射到MI中。使用不同的显色剂对组织进行顺序处理，以便在单个切片中观察到两种示踪剂。我们分析了同侧顺行标记的分布。每个皮质区域的纹状体标记基本上由一条宽的斑块状密集标记带组成，其间穿插着较浅的标记。SMA纹状体投射主要位于壳核内，从前连合水平分布到壳核的最后端。在中间水平，标记从壳核的腹外侧边缘向背内侧倾斜扩展，直至尾状核的外侧边缘。在壳核的相应部分观察到来自MI的标记，尽管SMA投射比MI投射更靠前且背内侧移位，并且来自SMA和MI的最重投射分别位于不同位置。基于双重顺行标记技术，我们发现主要在壳核中央部分，来自SMA和MI前肢代表区的投射有相当大的重叠。这些结果表明，SMA和MI的同源身体区域向纹状体的部分区域发出广泛且基本重叠的投射。
